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Efficient process for preparing an ester of a cellulose ether

a technology of cellulose ether and ester, which is applied in the direction of coatings, etc., can solve the problem of not being able to achieve homogeneous mixtures for an extended time period, and achieve the effect of stabilizing a reaction mixture comprising a cellulose ether

Inactive Publication Date: 2019-02-05
THE DOW CHEM CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

This approach allows for the production of esterified cellulose ethers with improved stirrability and reduced production costs by eliminating the need for drying and grinding, and enables the use of high viscosity cellulose ethers without the need for partial depolymerization, resulting in a more efficient and cost-effective process.

Problems solved by technology

While the esterification and partial depolymerization proceeded, the stirring ability of reaction mixture improved, but a homogeneous mixture could still not be achieved for an extended time period.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0096]512 g (5.0 moles) of acetic anhydride was loaded to a reactor and heated to 51° C. Then 128.97 g HPMC Wet Cake 1 (absolutely dry HPMC content 38.77%) was loaded in portions to the reactor under stirring. 128.97 g HPMC wet cake corresponded to 50 g HPCM, calculated on the dried basis, and 78.97 g (4.38 moles) of water.

[0097]Then the temperature was increased to 70° C. A slight exothermic reaction was observed, but no acetic acid or acetic anhydride was refluxed at the condenser. The complete HPMC was dissolved after 30 min without agitation issues (300 rpm). Then 14 g of succinic anhydride was loaded to the reactor (850 rpm) and after 10 min 50 g sodium acetate and 1.67 g of potassium chlorate were added. The temperature was increased to 85° C. (300 rpm) and the mixture was reacted for 3.5 h. Then the crude HPMCAS was recovered by precipitation with cold water and the product washed with hot water and filtrated several times.

example 2

[0098]279 g (11.53 moles) of acetic anhydride was loaded to a reactor and heated to 51° C. 99.21 g HPMC Wet Cake 2 (absolutely dry HPMC content 50.4%) corresponded to 50 g HPCM, calculated on the dried basis, and 49.21 g (2.74 moles) of water. Then the temperature was increased to 70° C. An exothermic reaction was observed, acetic acid or acetic anhydride refluxed at the condenser for a short time. The complete HPMC was dissolved after 30 min (100 rpm). Then the temperature was increased to 85° C. and 0.38 g of sulfuric acid solution in glacial acetic acid (a mixture of 20 g of 85% sulfuric acid and 80 g of glacial acetic acid) was added and the mixture was allowed to react for 30 min. To stop the degradation reaction 0.06 g of NaOH was added to the reactor. Then 14 g of succinic anhydride and 65 g of acetic anhydride was loaded to the reactor (850 rpm) and within 6 min 50 g sodium acetate was added. The temperature was increased to 85° C. (300 rpm) and the mixture was reacted for 3...

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Abstract

A process for producing an esterified cellulose ether can be efficiently be produced by reacting a moist cellulose ether having a water content of at least 10 percent, based on the weight of the moist cellulose ether, with an aliphatic monocarboxylic acid anhydride, a dicarboxylic acid anhydride or a combination thereof. Further improvements in efficiency and reduction in process steps are achieved in a process for producing an esterified cellulose ether which comprises the steps of a) reacting cellulose with an alkaline material to produce alkali cellulose, b) reacting the produced alkali cellulose with one or more etherifying agents and washing the produced cellulose ether to obtain a moist cellulose ether having a water content of at least 10 weight percent, and c) reacting the moist cellulose ether with an aliphatic monocarboxylic acid anhydride and / or a dicarboxylic acid anhydride and with a depolymerizing agent.

Description

FIELD[0001]The present invention relates to a process of improved efficiency for producing an ester of a cellulose ether by reacting the cellulose ether with an aliphatic monocarboxylic acid anhydride and / or a dicarboxylic acid anhydride.INTRODUCTION[0002]Esters of cellulose ethers, their uses and processes for preparing them are generally known in the art. Various known esters of cellulose ethers are useful as enteric polymers for pharmaceutical dosage forms, such as methylcellulose phthalate, hydroxypropyl methylcellulose phthalate (HPMCP), methylcellulose succinate, or hydroxypropyl methylcellulose acetate succinate (HPMCAS). Enteric polymers are those that are resistant to dissolution in the acidic environment of the stomach. Dosage forms coated with such polymers protect the drug from inactivation or degradation in the acidic environment or prevent irritation of the stomach by the drug.[0003]U.S. Pat. No. 4,226,981 discloses a process for preparing mixed esters of cellulose eth...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): C08B13/00C09D101/32C08L1/32
CPCC08B13/00C09D101/32C08L1/32
Inventor PETERMANN, OLIVERSPREHE, MATTHIASAPPELL, ROBERT B.
Owner THE DOW CHEM CO